“We can't comment on taxpayers due to disclosure laws,” said Lea Crusberg, an IRS spokeswoman for the southern Texas region.

Stack took off in his single-engine Piper Cherokee from Georgetown Municipal Airport at 9:40 a.m. Twenty minutes later, his plane crashed into the IRS building in north Austin that houses the criminal investigations unit, sparking a fire and sending two people to the hospital.

Stack, who died in the crash, was identified as the pilot who steered the plane into the IRS building.

The identity of the other person killed was not available but is believed to be an IRS employee who could not be accounted for earlier in the day.

Within hours of the crash, it was discovered that Stack's $232,000 home had been set on fire. The white garage doors on the two-story brick home appear to have imploded. The back of the house was blown away and smoke rose from the gutted residence for hours.

‘Following all of the rules'

Stack's mostly incoherent note, which railed against the U.S. tax system, capitalist greed, his accountant, former President George W. Bush and others, told how he came to Austin in search of work after spending the dot-com bust in the Los Angeles area.

Stack detailed how he was introduced to a group of people in the 1980s who told him of particular tax exemptions to take. He did so, and it later cost him dearly, according to his apparent suicide note.

“We carefully studied the law (with the help of some of the ‘best,' high-paid, experienced tax lawyers in the business), and then began to do exactly what the ‘big boys' were doing (except that we weren't steeling [sic] from our congregation or lying to the government about our massive profits in the name of God),” Stack wrote. “We took a great deal of care to make it all visible, following all of the rules, exactly the way the law said it was to be done.”

At the same time, Stack's own startups seemed to flop.

California state records reveal two failed startups by Stack. In 1985, he incorporated Prowess Engineering Inc., which was suspended two years later.

Music was a sideline

Until a few years ago, Stack played with the Billy Eli Band, a local Austin group. He told band members he left to spend more time at work at his software consulting business, Embedded Art.

“He played bass in my band for a while and recorded one album with me,” said Billy Eli. “Joe was a friendly, happy, easygoing guy. This is so hard to get my mind around because Joe was so normal. This was so totally out of character.”

Another band member, Jim Hemphill, said he saw Stack in the past six months and noticed no signs that he was distraught.

“I never saw anything like this in Joe,” Hemphill said.

As the National Transportation Safety Board officials began their investigation at the site of the crash, FBI officials swarmed the airport where Stack stored his plane and canvassed his neighborhood in search of more clues.

Stack's second wife, Sheryl, and 12-year-old stepdaughter, who were not in the home when it exploded and burned, spent hours with FBI officials in a nearby house Thursday.

Neighbors recalled how they heard the Strack house blow up. Dane Vick said he made a 911 call to report the fire after hearing an explosion about 9 a.m.

“You could see glittering in the air,” Vick said. “It was shattered glass hitting the ground.”

Vick said he ran over to the back fence of the home and started calling in, but no one appeared to be in the house. He said flames started coming out of the windows almost immediately.

Another neighbor, Elbert Hutchins, 67, said he first thought the commotion was from a wreck on a nearby major street. He and his wife, Carlotta, 66, ran out into the yard.

“You could already see flames coming out of the windows,” Hutchins said.

Another neighborhood resident, who would only give his name as Steve, said he met Stack on several walks around the neighborhood. He described Stack as a “brilliant” musician. He said Stack had been a private pilot for years.

“He was a nice guy. I enjoyed chit-chatting with him,” Steve said.

Natalie Kunkel, 39, who lives two doors down from the Stacks, said she used to go to the swimming pool with the wife and daughter, but she rarely saw the husband. Kunkel said the 12-year-old often came over to play with her Siberian husky, Dakota.

Family not commenting

A crowd gathered Thursday to watch the firefighters douse the blaze.

“Someone said they saw something on TV about a plane hitting an office building,” Hutchins said. He and his wife went back inside and turned on the television.

They had no idea the plane crash and the fire in the Stacks' home might be connected until later, when media and federal agents descended on their neighborhood.